Technically complex sewage plants are used in urban conurbations for the purification of household and industrial wastewater. In contrast, in rural areas, there is a need for cost-effective and ecologically compatible wastewater purification units, e.g., constructed wetlands, which may be incorporated into the landscape picture and operated in an environmentally compatible way.
Such constructed wetlands include, for example, the constructed wetland described in DE 42 25 699. The constructed wetland comprises a four-layer, vertically permeated earthen body, which is planted with reeds. The carbon degradation, the nitrification, and the phosphorous elimination occur by absorption in the earthen body in the first two layers. The nitrification is performed in the third layer. In addition, a straw carbon wastewater extract is introduced into the third layer as an organic carbon source. The layers are constructed from various materials and have differing homogeneity. The dwell time is achieved in that a backup is generated in the polluted water flowing from top to bottom.
A biopolder [intermediate bed] for the biological purification of soils and sludges is described in DE 43 23 610, in which an aerobic area and an anaerobic area are situated one above another. In the anaerobic area, nitrogen oxides are converted into nitrogen and oxygen and/or water by denitrifying microorganisms. The wastewater first permeates the aerobic area and subsequently the anaerobic area. The organic pollutants present in the soil or sludge, e.g., petroleum, are chemically converted by aerobic microorganisms. The pollutants or reaction products which are not converted in the aerobic area reach the anaerobic area and may be converted therein by further microorganisms. A water-permeable nonwoven material may be situated between the aerobic area and the anaerobic area. The upper area is formed by a soil or sludge layer and the anaerobic area by a drainage bulk product.
A vertical-horizontal filter unit for the purification of wastewater is described in DE 197 37 690. The unit comprises a lower filter zone and an upper filter zone. The upper filter zone may contain clay minerals and/or iron filings, and the lower filter zone comprises fine gavel and/or medium gravel and carbonaceous additives may be admixed therewith. A barrier layer having openings is located between upper filter zone and lower filter zone. A division into an aerobic area or an anaerobic area is not described.
The units described in the prior art have problems in regard to the achievability of an optimum metabolic performance for various reasons, in particular denitrification performance in the aerobic area. It is therefore desirable to provide a unit in which an increase of the metabolism, in particular the denitrification, may be achieved via suitable devices and measures, in order to thus eliminate pollutants and environmentally-harmful substances.
This object is achieved by a horizontal-vertical filter unit and a method described herein.